Spark pltig



June 30, 1936. A. A. KAs-RJIAN SPARK PLUG Filed July ll, 1929 Patented June 30, 1936 UNITED STATES PATENT OFFICE SPARK PLUG Armen A. Kasarjian, Philadelphia, Pa., assigner to Mosler Ignition Corporation, New York, N. Y., a corporation of New York Application July 11, 1929, Serial No. 377,5'2

4 Claims.

skilled in the art, but it may be briefly noted that sparking in the-plugv produces certain oscillations which are clearly audible in radio recep- 15 tion and not only seriously interfere with the reception of sound, such as voice transmission, but render the reception of code practically unintelligible.

The purpose or object of the present invention is to provide eiilcient plug construction which will be absolutely reliable for the performance of its intended functions in the ,ignition system and at the same time equally reliable, and durable and eiiicient in the elimination of interference with radio reception. So far as I am aware no such i structure has heretofore been suggested.

Speaking generally, the principle upon-which the present invention operates is the shielding of the oscillations within a metallic casing incor- -0 porated in the plug construction and the grounding of such casing with respect to the motor. The shielding to which I have referred directly Within the plug construction is of marked practical importance. Spark plugs intended for use in aviation must be reliable. They are generally designed to operate under predetermined conditions and if these conditions are departed from, the plug will not properly operate. For example,

questions of heating and cooling, i. e., the opera? tion under predetermined temperatures', `is of marked importance in spark plugs and if an attempt is made to employ shielding devices extraneous of the plug construction, it is found that the characteristics of lthe plug and its operative conditions are so varied as to seriously interfere with the reliability of the plug.

Y A serious'problem incident to the incorporation of shielding in plug construction is the question of proper protection of the insulation and morel particularly the insulation employed in the spark plug leads. Such insulation must be absolutely reliable and a breaking down thereof will cause the cessation of the operation of the plug. Heat in the plug is rather a serious factor to be considered in this connection andthe proper safe- Y Ci guarding of the insulation of the lead to the plug and the connection between the plug'and the lead is of marked importance.

l The plug of the present invention satisfactorily solves the foregoing problems and provides an ab- 5 solutely reliable construction from the standpoint '"3 of ignition and a thoroughly eiiicient const-ruction insofar as the elimination of disturbances in radio reception is concerned. Speaking generally, the plug of the present invention embodies 1,0 a metallic envelope which completely envelops the interior plug parts in such a manner that the current to the insulated electrode is fed to the gap through an uninterrupted metallic shield and those parts which carry the current arev so 1f? heat insulated as to adequately protect the insulation of the current lead and preclude the breaking down thereof under long continued service.

Features ofthe invention, other than those 20 specified, will be apparent. from the hereinafter 5? detailed description and claims, when read in conjunction with the accompanying drawing.v

' The accompanying drawing illustrates one practical embodiment of the invention, but the l25 construction therein shown is to be understood as illustrative, only, and-not as defining the limits of the invention. I

Figure 1 is a central vertical section through a plug embodying the present invention showing 30 the parts in assembled rela-tion. r r l Figure 2 is also a vertical central section of the parts of the plug, but showing the parts separated from one another in order to more clearly illustrate the parts individually and to show the 35 manner in which they are assembled.

The plug of the present invention embodies the usual metal shell l having the exteriorly threaded shank 2 adapted to be screwed into the spark plug hole of an engine cylinder. The upper 4,0

portion of the shell is interiorly threaded as shownv at 3 to receive a carrier bushing 4 on which the central electrode and cooperating insulating parts are supported.' The interior of the bushing 4 is stepped to provide the shoulders 5, 6, f1.5 and 'l positioned respectively one above the other. The two shoulders 5 and 6 face in an upward direction, while the shoulder 1 faces in a. downward direction and above the shoulder 5 the interior of the bushing isf threaded as indicated at 8. I wish to call attention to the fact that between the seats 5 and 6, the interior of. the bushing tapers or converges in a downward direction as indicated by the tapered face 9.

` The central electrode designated I0 is. in `the 55 2 accessi.

forni oil rnetal oar or rod provided its loottioned on the seat En and thereafter a metallic toni n an enlarged head il, the upper lace U2 of which constitutes a shoulder or seat on= nosed to the 'l oi the bushing. The il preferably aria-lig; bored to receive a sparking point c i3 `waited for cooperation with the point l@ or the shell E under= derstood that the particular type oi points used the nlug of this invention is immaterial. They may be changed and modied without arting iront the inventlo l@ is 1@vided near upper end a relatively eatelsive annular channel which renders a portion of the bar intermediate its ends or reduced cross section, as clearly shown in '.llfie upper end of the 2 preferably tanned to receive adjusting screw the tourcose or 'which will be hereinafter more fully exil] indicates an insulating sleeve which. in nractice, conveniently be iornied troni cigarette although other suitable insulating rnaterlal may be employed in this connection. This insidating sleeve is adapted to be embraced lor a T@dition oi its length by a metallic packing sleeve i0, practice may be conveniently made or and the sleeve ill is in turn embraced by an wedge i9, the inner lace or which wedge cylindrical, while the outer lace ,is

assembled about the lower end of the sleeve to y give the desired thiclrne. Thereafter the upper end or the rod' l@ is passed upwardly through the metal carrier bushing il, so that the upper end of the rod and sleeve il entend well up into the interior of said bushing. The metallic packing sleeve l@ is then passed downwardly overthe sleeve [Il and comes to rest on the seat 6. Next the wedge UQ is 'passed downwardly over the metal packing sleeve i8 until it cornes into engagement with the tapering surface Q of the bushing. Sucient axial pressure is thereupon exerted on the bushing t and rod l@ in opposite directions to firmly compress the washers 2@ between the seats 'l and l2. This having been accomplished, the parts thus assembled are held stationary, while the wedge l@ isq'rorced downwardly with sufficient pressure towlorce that portion of the sleeve il winch overlies the annular channel le' into close conformity with said channel as indicated in Fig. l. The intermediate metal packing sleeve 08 is ,simultaneously correspondingly shaped,`V so that by the time the wedge has been forced to its nalposition indicated in Fig. l., both the sleeve i8 and bushing il will conform to the adjacent contour of the rod lli and thus constitute with the' sleeve is screwed into cooperation with, the' or the bushing (i. Previous to the at tachrnent of this sleeve, however, there is formed within the sanne an insulating sleeve of cigarette 2i. This may be accomplished by forming the sleeve 2l on a suitable mandrel and thereafter slipping the sleeve 23 over the thus formed tsleeve 2l.

lt will noted that the upper edge of the sleeve 2l fits into an annular groove in the sleeve and the sleeve 2l is thus maintained intact dining the assembly operation. A few additional insulating washers. 22o are thereafter introduced weerlthe lower margin or the sleeve 2l and the meer margin of the sleevel'l. nliter the sleeve has been tightly screwed into place, the upper edge of the bushing l is spun in as shown at la render the assembly permanent.

sleeve 23 while relatively thin lor the part oi its length is provided at its botan enlargement thereon threaded to coact the interior threads of the bushing fl, and as the metal sleeve 23 is screwed down tight, it clamps the washers to the seat o and simultaneously mounts the metal sleeve 23 in position on the bushing. The upper portion of the bushing is slightly enlarged to provide an exterior cylindrical contour lll at the base of which is a shoulder and said rnetal. sleeve is inwardly danged at its top as indicated at 2li to overlie the upper end or the insulating sleeve ill.

These parts having been assembled as stated, the threaded. shank of the bushing l is screwed into the threads 3 of the shell to act upon an intermediate gasket 2l! as indicated in Fig. l and to mount the bushing on the shell. This completes the assembly operation of the plug.

will now describe the manner whereby a spari:

plug lead is associated with the plug as thus fardescribed. The lead wire is indicated by the reference character llt is provided with suitable insulation, suolo-as the rubber insulation t@ with the fabric covering 3@ and over this fabric covering maybe provided a suitable metal armor i The end of the ignition lead is adapted to extend into insulating terminal 32 which may be of loalrelite or ceramic composition or of any other suitable insulating substance. IThis terminal has an. over-all exterior diameter substantially equal to the interior diameter of the insulating sleeve 2l and being provided at its bottom with'a depending portion 38 of decreased cross section substantially equal to the interior diameter of the insulating sleeve ill. The insulating terminal 32 is cored to two diameters, the upper portion being sciently large to receive the wire 28' with the' insulation 2Q. and t@ as indicated in Fig. 2, While the smaller diameter 'for the remainder of the length or the terminal is of just sufiicient size to permit the bare wire 2d to extend therethrough.

lt is convenient to rivet over or flatten out the' end of the wire at the end of the terminal over a metal Washer 34a as shown at 36 and if stranded wire is used as usually, the part 34 is preferably silver soldered to the washer to provide a good terminal contact. The shape and proportion of the 'parts are such that the terminal 32 may be passed downwardlythrough the insulating sleeve` 2l until the contact 36 at the end of the lead wire engages with the adjusting screw i6 in the upper end of the rod l@ which carries the insulated ,electrode i3. Threaded on to the terminal 32 is a cap 35 which seats on the top of the sleeve 23 -enu'tne screw le n to provide for such adjust- 75' mentas will insure proper contact when the cap is substantially seated on said sleeve. In lieu of the screw I6, 1 may mount a coil spring on the contact 34 to yieldably engage the rod ID.

A clamping member mounted on the cap 35 embodies a plurality of depending spring arms 36 which when the cap is seated on the sleeve 23 will grip beneath the shoulder 25 as shown in Fig. 1 to hold the lead in position. The lower ends of these spring arms are preferably bent inwardly and then outwardly to give the desired grip to hold the lead in position and by so forming these fingers, they may be wired with safety Y wire to lock them in position if desired. A cu.sh'

ion Washer of leather or the like 36a may be interposed between th'e cap and sleeve to make a Weather tight joint. l

It will be noted from Fig. 2 that the armor 3| for the cable will extend into the upper end of the cap 35 and may be anchored therein in any suitable manner. The upper end of the cap 35 is preferably so formed that after the armor of the cable has been introduced into the cap as shown, the overlying portion of said cap can be contacted or forced in an inward radial direction to grip the armor tight and produce a Weather proof joint, i

It may be here noted that the insulating sleeve 2l has a dual function in that it not only insulates the terminal 32 from heat in the sleeve 23, 'but it also serves as a protectionary electrical insulation in the event that other insulation of the piug breaks down.

It will be noted from the foregoing detailed description that the exterior of the assembly is wholly. metallic. In other words, the plug is entirely shielded and all of this shielding is grounded with respect to the shell I which is in turn grounded with respect to the motor. The exterior surfaces of the plug embody the outer surfaces of the shell l, carrier bushing 4, metallic sleeve 23, cap 5 and the armor 3l of the cable. .In other words,.the entire exterior of the plug constitutes a metal shield grounded on the engine. It will be noted, however, that the insulation is so disposed and proportioned that it will not only properly insulate electrically, but it will properly protect the insulation 29 and 30 of the ignition lead against undue heat. This is a very important fact for unless the insulation of the lead is properly safeguarded against heat, the plug will not function for any appreciable period before this insulation breaks down.

Exhaustive tests have shown, however, that with a plug as described, the insulation 29 may be of rubber, because it is not subjected to seriously high temperatures. The wall of the sleeve 23 is, in the main, relatively thin and much heat which may be conducted upwardly from thel shell through the bushing to this part is dissipated at this point without the transmission of this heat to the ignition lead. By thoroughly shielding the plug as stated, the oscillations of the spark are grounded by means incorporated directly in the plug structure and thus the efliciency of the plug from the standpoint of ignition is eifectually maintained. v

The accompanying drawing shows the invention in its preferred practical form, but the invention is to be understood as fully commensurate with the appended claims.

Having thus fully described the invention, what I claim as new and desire to secure by Letters Patent is:

l. A spark plug embodying a tubular metallic part, the bore of which has an outwardly flaring wall, a central electrode extending axially through said part and having a reduced cross section for a portion of its length, an insulating sleeve embracing the central electrode, a metal sleeve embracing the insulating sleeve, and a tubular wedge interposed between the aring wall and the metallic sleeve and engaging said wall' with sufficient force to press the metallic and insulatingsleeves into conformity with the reduced portion of the central electrode for the purpose of making a gas tight joint and to secure the electrode against. relative longitudinal movement with respect to the metallic part of the plug.

2. A spark plug embodying central electrode provided with a coaxial annular channel, a tubular metallic shell embracing said electrode and spaced therefrom, said shell having a frustroconical bore juxtaposed with said channel, an insulating sleeve embracing the electrode, a gripping sleeve embracing the insulating sleeve, and a tubular wedge interposed between the gripping sleeve and the frustroconical bore of the shell and n engaging said bore with suflicient force to press the gripping and insulating sleeves into conformity with the channel of the electrode to form a gas tight joint and lock the electrode within the shell.

3. A spark plug embodying a bushing provided therein with a central opening therethrough, a center electrodel passing through said opening and having an annular channel arranged within the opening and spaced from the walls of the latter, an insulating sleeve embracing the center electrode within said opening, a gripping sleeve embracing the insulating sleeve within the opening, and tubular wedging means interposed between the gripping sleeve and the wall of the opening and engaging the latter with sufficient force to press the gripping and insulating sleeves into conformity with the channel of the electrode to form a gas tight joint. and lock the electrode within the bushing. v

4. A spark plug embodying a bushing provided therein with a central opening therethrough, a center electrode passing through said opening and having an annular channel arranged within the opening and spaced from the walls of the latter, an insulating sleeve embracing the center electrode within said opening, a gripping sleeve embracing the insulating sleeve within the opening, and tubular wedging means interposed between the gripping. sleeve and the wall of the opening and engaging thelatter with sufficient 

